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]]>The post How accurate are the coronavirus tests used in the U.S.? appeared first on Virus Reports.
]]>Months into the coronavirus outbreak, no one really knows how well many of the screening tests work, and experts at top medical centers say it is time to do the studies to find out.
When the new virus began spreading, the Food and Drug Administration used its emergency powers to OK scores of quickly devised tests, based mainly on a small number of lab studies showing they could successfully detect the virus.
That’s very different from the large patient studies that can take weeks or months, which experts say are needed to provide a true sense of testing accuracy.
The FDA’s speedy response came after it was initially criticized for delaying the launch of new tests during a crisis and after the Centers for Disease Control and Prevention stumbled in getting its own test out to states.
But with the U.S. outbreak nearly certain to stretch on for months or even years, some experts want the FDA to demand better evidence of the tests’ accuracy so doctors know how many infections might be missed.
There have been more than 2 million confirmed coronavirus cases in the U.S. and more than 115,000 deaths, according to data compiled by Johns Hopkins University. Cases in nearly half of U.S. states are rising.
In recent weeks, preliminary findings have flagged potential problems with some COVID-19 tests, including one used daily at the White House. Faulty tests could leave many thousands of Americans with the incorrect assumption that they are virus-free, contributing to new flare-ups of the disease as communities reopen.
“In the beginning, the FDA was under a lot of pressure to get these tests onto the marketplace,” said Dr. Steven Woloshin of Dartmouth College. “But now that there are plenty of tests out there, it’s time for them to raise the bar.”
The FDA said in a statement that it has already asked multiple test makers to do follow-up accuracy studies, although it didn’t say for how many of the more than 110 authorized screening tests. The agency also said it is tracking reports of problems. Accuracy has also been an issue with blood tests that look for signs of past infections.
No screening test is 100% accurate. So details on accuracy are routinely provided for tests of all types, including seasonal flu, hepatitis, HIV and cancers. For example, rapid flu tests are known to miss 20% or more of all cases, a factor doctors weigh when treating patients who have symptoms but test negative.
For now, most COVID-19 tests in the U.S. don’t give data on real-world performance, including how often the tests falsely clear patients of infection or falsely detect the virus. That information is lacking for all but a few of the roughly 80 commercial screening tests available, according to an Associated Press review.
The government’s emergency authorization process “requires a lower level of evidence,” the agency said. Makers need only show that a test “may be effective” instead of the usual requirement to demonstrate “safety and effectiveness.” They would have to meet that higher threshold once the U.S. government declares the emergency over.
Many of the commercial test makers submitted results from 60 samples, the minimum number required and mostly used lab-produced specimens of the virus. The FDA now recommends the use of nasal swabs or other real samples from people screened for coronavirus.
Experts say larger patient studies patients are needed to assess a test’s true performance.
Lab testing bears little resemblance to actual — sometimes imperfect — conditions at hospitals, clinics and testing sites noted Dr. Robert Kaplan of Stanford University.
“You’re testing people in parking lots, the patients themselves are extremely anxious and often unable to follow instructions,” said Kaplan, a former associate director of the National Institutes of Health.
Kaplan and others say those differences could explain why some tests are not performing as expected.
Last month, the FDA warned doctors of a potential accuracy problem with Abbott Laboratories’ rapid ID Now test, which delivers results in roughly 15 minutes. The test has been lauded by President Donald Trump and used to screen the president, his staff and visitors to the White House.
The FDA alert followed a preliminary report by New York University that found Abbott’s test missed between a third to one-half of infections caught by a rival test in patients screened for the virus.
Abbott rejected the findings, saying the researchers did not follow the instructions for using its test. The company pointed to alternate patient studies, including its own, that have found the test successfully detects between 91% and 95% or more of virus cases when compared to other tests.
But similar problems with ID NOW’s accuracy have been flagged in preliminary reports by researchers at Stanford University, Loyola University and the Cleveland Clinic.
For now, the FDA is requiring Abbott to conduct follow-up studies in several different patient groups.
The FDA’s emergency standards “are still high but there is a significant difference in the body of work that what would go into a submission under the normal process,” said Abbott vice president John Hackett. “Our normal process takes years to bring these out.”
Requiring bigger studies of all coronavirus tests could provide valuable information, but it could also strain the FDA’s already stretched staff and resources, said Dr. Daniel Schultz, former director of the FDA’s medical device center.
Dr. Colin West of the Mayo Clinic worries doctors and patients have put too much confidence in the current crop of tests, when an unknown number of patients with COVID-19 are likely receiving false negative results.
Even a modest error rate can have grave consequences during an outbreak like COVID-19. West gives the example of a test that is 95% accurate at detecting the virus and is used on 1 million people. That would still result in 50,000 people being incorrectly told that they don’t have the virus.
“The negative test does not mean that I’m off the hook,” West said. “We just need to maintain that level of vigilance until we have a better sense of how good these tests really can be.”
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]]>The post These are most — and least — accurate COVID-19 tests appeared first on Virus Reports.
]]>By Eric Ting, SFGATE
Published
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UCSF scientists process COVID-19 test samples at a new UCSF diagnostic laboratory adjacent to the Chan Zuckerberg Biohub (CZ Biohub) on Friday, April 24, 2020, in San Francisco.
UCSF scientists process COVID-19 test samples at a new UCSF diagnostic laboratory adjacent to the Chan Zuckerberg Biohub (CZ Biohub) on Friday, April 24, 2020, in San Francisco.
Photo: Noah Berger For UCSF
Photo: Noah Berger For UCSF
UCSF scientists process COVID-19 test samples at a new UCSF diagnostic laboratory adjacent to the Chan Zuckerberg Biohub (CZ Biohub) on Friday, April 24, 2020, in San Francisco.
UCSF scientists process COVID-19 test samples at a new UCSF diagnostic laboratory adjacent to the Chan Zuckerberg Biohub (CZ Biohub) on Friday, April 24, 2020, in San Francisco.
Photo: Noah Berger For UCSF
As both active virus and antibody testing ramps up across the country, it will soon be relatively easy for individuals to get tested, regardless of if one is displaying COVID-19 symptoms.
If you plan to get a test — either antibody or active virus — here is what you should know about the accuracy of the results.
Active virus testing (Diagnostic or PCR test)
The most widely available form of testing is PCR (polymearse chain reaction) testing, which detects if an individual is currently infected with the coronavirus.
Cleveland Clinic researchers tested 239 specimens known to contain the virus using some of the most commonly used coronavirus PCR tests. Here are the findings for each:
The CDC-developed test, which returns results in a few days, detected 100% of positive samples. A similar test from Roche detected 96.5% of samples, and a test from Cepheid that produces results in less than hour detected 98.2% of positive samples. However, Abbott’s ID NOW test — one that returns results in less than 15 minutes — detected virus in only 85.2% of positive samples, meaning it had a false negative rate of 14.8%.
Dr. Gary Procop, the head of the study, told NPR a test should be at least 95% reliable.
“So that means if you had 100 patients that were positive, 15% of those patients would be falsely called negative,” he said. “They’d be told that they’re negative for COVID when they’re really positive. That’s not too good.”
Abbott defended the test, and said potential problems could stem from storing samples in a solution called “viral transport media” before insertion into the testing machine. The company advocates for placing samples directly into the testing machine to ensure the most accurate results.
Generally speaking however, most PCR tests are considered to be very reliable.
Antibody testing
Considerably less reliable are antibody tests, which detect past infections by seeing if an individual’s immune system has developed protective antibodies.
The FDA has issued emergency approval for the production of several antibody tests, but the agency is now tightening regulations on approval given the unreliability of existing tests. Unlike PCR testing, where false negatives are what give scientists the most worry, antibody tests should strive to avoid false positives as it is more dangerous to tell an individual he or she has COVID-19 antibodies — and may have immunity — when that is not the case.
In a study of 14 of the approved tests, one of the tests gave false positives more than 15% of the time, and three others gave false positives more than 10% of the time.
“That’s terrible, said Dr. Caryn Bern, one of the study’s authors. “That’s really terrible.”
Three different tests had false positive rates of 1% or less, but all had false negative rates of over 10%, meaning they failed to detect antibodies in at least one of 10 actual infections. Observers concluded that none of the currently widely available antibody tests can be considered completely reliable as a result.
“Those numbers are just unacceptable,” Scott Hensley, a microbiologist at the University of Pennsylvania, told the New York Times. “The tone of the paper is, ‘Look how good the tests are.’ But I look at these data, and I don’t really see that.”
Earlier this week, a new antibody developed by Roche was approved by the FDA, and is considered to be the most accurate antibody test developed to date. Roche states the test detects antibodies with 100% accuracy, and has a false positive rate of just 0.2%.
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Eric Ting is an SFGATE digital reporter. Email: eric.ting@sfgate.com | Twitter:@_ericting
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]]>Coronavirus antibody testing is supposed to tell who’s been exposed to the virus, but questions have risen about how accurate they are and how much protection those antibodies provide. Meanwhile, the World Health Organization is warning officials that they should not use these tests to provide so-called “immunity passports.”
Finding out who has been exposed to the coronavirus has been identified as a key to reopening the country. But there are problems.
The WHO said there’s no guarantee of immunity after infection but here in the U.S., medical experts overwhelmingly agree that the antibodies that remain give some level of protection.
“So the tests that we have now on the market … Don’t tell you individually whether you have the neutralizing antibodies, whether you have the antibodies that can prevent you from getting an infection again,” CBS News medical contributor Dr. David Agus said.
Of the more than 160 antibody tests flooding the market, the FDA has only given emergency use authorization to eight.
Bioengineer Patrick Hsu from U.C. Berkeley and colleagues set out to see how many are accurate. Results so far are mixed.
“There are definitely some that are better than others,” Hsu explained. “We see out of the 10 we tested … I think that’s three that after two weeks were 90% positive.”
Along with new symptoms, there are new clinical trials.
The Feinstein Institutes for Medical Research at Northwell Health is quietly testing the acid reflux medication Pepcid, also known as famotidine, to see if it blocks the virus from replicating.
“We don’t know if taking famotidine causes more harm than good,” Dr. Kevin Tracey, president of the Feinstein Institutes, told CBS News. “We will be studying hundreds of patients who are hospitalized, receiving intravenous famotidine.
Researchers are currently studying whether acid reflux medication helps treat the coronavirus. Right now, there’s no evidence that it does. Doctors stress the potential dangers in misusing drugs — prescription or over the counter. Bottom line: always consult your physician.
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